Antireflective coatings (ARC) are one of the essential materials used in microlithographic process. Typical ARC materials are expected to offer at least one of the following advantages: controlling line width by reducing swing curve; reducing standing wave reduction, planarization, minimizing reflective notching. As the patterning feature size shrinks to sub-65 nm in the microelectronic industry, tremendous challenges for new materials have been confronted to the materials industry. Among one of them is the 193 nm antireflective coatings (ARC), because the 193 nm photoresists have a very thin layer in order to get the right depth of focus and resolution and do not offer sufficient light absorption and etch resistance. There are three different types of materials for 193 nm ARC applications: inorganic, organic, and silicon-based materials. Inorganic based materials generally contain silicon oxynitride (Si—O—N), silicon nitride (Si—N), and silicon carbide. Because they are oxidized into silicon dioxide in oxygen plasma, these inorganic based materials have excellent oxygen etch resistance. However, because these materials are produced using chemical vapor deposition (CVD), they can not be used for patterning planarization. In addition, typically, these materials cannot be removed with typical etchants unless a harsh etching condition is used. Thus, they are generally retained in a device. On the other hand, the organic based ARC materials are spin-on based materials and thus can be used for patterning planarization. They are reworkable with typical etchants. However, they do not offer high oxygen etch resistance. Moreover, because photoresists and organic ARC materials are both organic materials, organic ARC materials do not offer CFx plasma based etch selectivity required for stripping off ARC layer. The silicone based ARC materials are silicon based spin-on materials. They are expected to have advantages of both CVD and organic ARC materials.
There are many challenges for making Si based ARC materials. The materials need to have appropriate refractive index (n) and coefficient of absorption (k) at 193 nm to match with the photoresist. The materials need to be curable in 1 min by UV or heating at temperatures lower than 250° C. for fast turn around processing. The material needs to be compatible with photoresist but no intermixing and/or diffusion occur(s) so that no scum and footing appear in a device with a small feature size. Further, the material needs to be resistant to propylene glycol methyl ether acetate (PGMEA), other typically photoresist solvents, and bases such as tetramethyl ammonium hydroxide (TMAH) after cure so that the thin film can withstand later processes. The film also needs to be reworkable for removal of the materials. Finally, the materials must be very stable at room temperature for at least three month with no significant molecular weight growth.
Si—H containing materials are essentially base and HF buffer solution soluble and thus the Si—H containing materials used for ARC applications are potentially reworkable. Si—H containing silsesquioxane resin such as THTMe and THTPh can be cured at low temperature and Si—H containing silsesquioxane resins such as THTMeTPhTR where R is a polyether group or an ester group, have potential as antireflective coating materials. Desirable properties in ARC resins include being polar to have better compatibility with a photoresist and an organic carbon underlayer, having a silicon content >30 wt % in order to get high oxygen plasma etch resistance and high CFx plasma etch selectivity and the functional groups on the resin need to be relatively small to mitigate the outgassing problems and porosity problems. It has now been found that resins that have an aryl sulfonate ester group are useful in ARC applications.